Various hollow fiber membrane fluid separation devices have been used for separating fluid mixtures. Normally, these fluid separation devices are designed so that a fluid mixture can be brought into contact with the hollow fiber membrane therein under pressure for permeation of one or more components of the fluid mixture. Upon contacting, the hollow fiber membrane allows the more readily permeable component of the fluid mixture to permeate into the permeate side of the hollow fiber membrane while retaining a substantial portion of the less readily permeable component of the fluid mixture on the non-permeate side of the hollow fiber membrane. The permeated and non-permeated components are removed through or recovered from at least one permeate outlet and at least one non-permeate outlet, respectively.
In some instances, fluid separation devices are designed to provide a purge or sweep fluid in the permeate side of the hollow fiber membrane. The use of a purge or sweep fluid on the permeate side of the hollow fiber membrane is beneficial in certain gas separation processes, such as gas dehydration processes, where because of high gas permeability coefficient of the permeated component(s), such as water vapor, a high permeate partial pressure builds up on the permeate side of the membrane. Since the high permeate partial pressure of the permeated component will limit the permeation and separation potential of the hollow membrane fibers in the fluid separation device, the introduction of a purge or sweep fluid having low partial pressure into the permeate side reduces the partial pressure of the permeated component, thus allowing the fluid mixture to be more thoroughly stripped of the more readily permeable component.
The fluid separation devices useful for providing a sweep or purge gas generally comprise an annular hollow membrane fiber bundle in a shell having a fluid feed inlet, a non-permeate outlet, a permeate outlet and a sweep or purge gas inlet. U.S. Pat. Nos. 3,499,062, 4,718,921, 5,108,464 and 5,026,479, for example, disclose such fluid separation devices. These fluid separation devices, however, require external plumbing and valves to regulate the flow of the sweep gas to be fed to the sweep or purge gas inlet port. The need to manifold the sweep or purge gas external to the fluid separation devices adds to the size and complexity of the fluid separation devices.
Accordingly, it is an object of the invention to provide means by which the operation of the fluid separation devices can be carried out without external plumbing and valves.
It is another object of the invention to provide means by which the fluid separation devices having a purging means can be easily implemented and operated.